The present invention relates in general to fluidized bed boilers, and in particular, to a new and useful apparatus and method for supplying cooling liquid to the interior of the heat exchanger tubes for a fluidized bed boiler under emergency conditions to avoid rapid depressurization and thermal shock.
Once-through circulation of fluidized bed boilers requires an inventory system to maintain coolant in the event of a loss of normal coolant flow. A standby pump and storage tank for supplying coolant to the economizer of a boiler has been proposed in the past. However, rapid depressurization and thermal shocking when using low temperature coolants present a problem in that damage is likely to result to the heat exchanger tubes and attached components.
A Babcock and Wilcox Technical Paper entitled "The Fast Fluidized Bed-A True Multi-Fuel Boiler" by L. Stromberg et al presented to The Eighth International Conference of Fluidized-Bed Combustion, Houston, Tex., Mar. 18-21, 1985, discloses the structure and operation of a fast fluidized bed boiler utilizing enclosure wall, bed, superheater and economizer heat exchangers.
U.S. Pat. No. 4,563,267 to J. J. Graham et al discloses the problems of thermal shock for the steam generator coils of a fluidized bed reactor when the reactor is subjected to load changes.
A Babcock and Wilcox Technical Paper entitled "The Babcock & Wilcox Atmospheric Fluidized Bed Combustion Development Program" by J. W. Smith, presented to The Southeastern Electric Exchange, 1982 Annual Conference, Kissimmee, Fla., Apr. 21-23, 1982, discloses the structure and operation of atmospheric fluidized bed combustors. According to this technical paper, the fluidized bed in such combustors is at a temperature range of 1,500.degree. F. to 1,600.degree. F.
Fluidized bed combustors having tubular heat exchangers at various locations throughout the combustion gas flow path, as well as on the enclosure walls of the combustor are disclosed in U.S. Pat. No. 4,542,716 to J. Dreuilhe et al and U.S. Pat. No. 4,614,167 to J. Bergkvist.